The research team, led by Alexandra M. Kortsinoglou and Vassili N. Kouvelis of the National and Kapodistrian University of Athens together with collaborators from Austria and Switzerland, focused on two commercially exploited species with fundamentally different lifestyles. Beauveria bassiana is a cosmopolitan generalist with a global distribution, capable of infecting economically important pests across multiple insect orders — thrips, whiteflies, spider mites and aphids among them — and frequently recovered as an endophyte or epiphyte living inside plant tissues, where it promotes growth and shields crops from disease. Beauveria brongniartii, by contrast, is a specialist whose virulence is aimed chiefly at soil-dwelling beetle larvae, most notably the European cockchafer Melolontha melolontha, a destructive scarab pest of central European agriculture, with only limited evidence that it can colonize plants.

To find the genomic signatures of this ecological split, the researchers sequenced the genome of the commercial B. brongniartii strain BIPESCO2, originally isolated from a cockchafer in Austria, and that of B. bassiana strain ATHUM 4946, retrieved from air samples in Athens. Sequencing was performed on the Oxford Nanopore MinION platform — using the higher-accuracy R10.4.1 flow cell chemistry for BIPESCO2 and R9.4.1 for ATHUM 4946 — with basecalling handled by Guppy’s super-accurate model. The resulting long reads were assembled de novo with Flye, polished through successive rounds with Racon and Medaka for BIPESCO2 and corrected with Canu for the B. bassiana strain, and annotated through the GenSAS v6.0 pipeline, which combined ab initio predictions from Augustus and GeneMark-ES with protein and transcript alignments to build consensus gene sets.

The quality of the resulting assemblies matters, because B. brongniartii has long suffered from fragmented genomic references. The BIPESCO2 assembly came out at 34.2 megabases in just ten contigs, with a contiguity N50 of 1.95 megabases and a longest contig of 3.69 megabases — figures comparable to reference-grade Beauveria genomes. Independent quality checks were rigorous: Inspector found no structural errors such as inversions, collapses or misjoins; 99.96 percent of reads mapped back to the assembly; and the estimated consensus accuracy of 99.99 percent (quality value 40.6) came at a mean sequencing depth of 124-fold. The official protein set scored 98 percent completeness against the Hypocreales BUSCO lineage dataset. The B. bassiana ATHUM 4946 assembly, at 34.7 megabases across 11 contigs with an N50 of 4 megabases, reached 95.7 percent BUSCO completeness. Both assemblies were deposited in the European Nucleotide Archive.

Armed with these reference-quality genomes, the team widened the lens to 20 genomes in total — 18 B. bassiana strains selected from 206 publicly available assemblies based on contiguity thresholds, plus two B. brongniartii strains — and carried out genome-wide orthology inference. Nearly all genes, 200,848 of them, sorted into 11,642 orthogroups, and the core genome proved vast: 8,032 orthogroups contained representatives from every strain, and 7,425 of those were strictly single-copy. Phylogenetic analysis of single-copy orthologues, rooted with two Cordyceps outgroups, cleanly separated the two species into distinct, well-supported clades. Applying a strict specificity criterion — a gene family present in all strains of one species and absent from all strains of the other — the researchers identified 201 B. bassiana-specific and 244 B. brongniartii-specific orthogroups. Notably, these lineage-restricted families were heavily divergent at the sequence level, with large fractions lacking recognizable conserved domains altogether, a hallmark of rapid evolution at host-interaction loci.

The functional flavor of those species-specific genes was telling. In B. bassiana, the generalist, the unique repertoire leaned toward broad metabolic versatility and stress tolerance: protein-binding domains, transmembrane transporters, monooxygenases and oxidoreductases, protein kinases, and a mix of peptidases including M35 deuterolysins and M60 metalloproteases capable of breaching the insect peritrophic membrane. There were also expanded multidrug-efflux transporter families of the MFS class, detoxification systems, and — strikingly — a single-copy orthologue encoding a Delta-endotoxin CytB-like protein, homologous to the pore-forming toxins of Bacillus thuringiensis. B. brongniartii, meanwhile, carried a narrower but more specialized toolkit: FAD-dependent oxidoreductases, O-methyltransferases, chitin- and carbohydrate-binding modules such as LysM and CFEM, an Egh16-like domain known from appressorium-specific virulence in plant pathogens, Tryp_SPc serine proteases targeting the cuticle, and a wide range of nutrient, ion and heavy-metal efflux transporters. Among its unique genes were an Rhs-associated toxin module previously known mainly from Gram-negative bacteria, an enterotoxin-like protein shared with Cordyceps militaris, and a polyketide synthase found so far only in one C. militaris strain.

Carbohydrate-active enzymes told a different story — one of remarkable conservation. Across all 20 genomes, 150 CAZyme families were shared, with minimal differences in copy number, indicating that both the generalist and the specialist retain a versatile enzymatic toolkit suitable for plant association, saprotrophy on dead organic matter, and insect pathogenicity alike. The chitin-cutting GH18 family, essential for degrading the insect cuticle, was the most expanded, with 271 proteins across the dataset, each strain carrying 13 or 14 copies, often decorated with chitin-binding CBM18, CBM1 or LysM modules that enhance substrate recognition and may help shield the pathogen from host immune detection. Chitin deacetylases that convert chitin to less recognizable chitosan were universally present. Yet within the conserved backdrop, a few families varied consistently between species: B. brongniartii possessed an extra GH27 α-galactosidase lacking the CBM13 binding domain found in its fused counterparts, more copies of AA7 flavin-dependent oxidases, and — uniquely among all Beauveria genomes examined — a PL20 polysaccharide lyase family encoding alginate and uronate-cleaving enzymes, hinting at a distinct substrate niche.

The sharpest species-level differences emerged in secondary metabolism. Each Beauveria genome carries on average around 46 biosynthetic gene clusters, and network analysis grouped the 922 clusters across the dataset into 105 gene cluster families, of which 25 formed the genus-wide core — including the genes for the insecticidal cyclodepsipeptides bassianolide and beauverolide, the antimicrobial pigment oosporein, and several siderophores. But on top of that shared core, B. brongniartii had expanded its arsenal of type I polyketide synthase clusters, with 11 copies compared to 6 to 9 in B. bassiana, and harbored six species-specific clusters, mostly predicting novel, heavily oxygenated polyketides, plus a terpene cluster complete with a squalene synthase and tailoring machinery. Even more intriguing were the structural remodelings of shared virulence clusters. In the beauverolide cluster, B. brongniartii has lost the phenylalanine-specific adenylation domain and the terminal D-isoleucine module of its nonribosomal peptide synthetase, and has swapped the Fe(II)-dependent hydroxylase of B. bassiana for an N-monooxygenase — a coordinated enzymatic substitution predicted to yield less hydroxylated, more hydrophobic beauverolide analogues. The bassianolide cluster, too, showed extensive rearrangement of tailoring enzymes between the two lineages, and the beauvericin cluster, intact in B. bassiana, exists in B. brongniartii only in truncated, likely nonfunctional form.

Effector proteins — secreted molecules that modulate host immunity — followed the same pattern of a conserved core with lineage-specific embellishments. Using signal peptide prediction, transmembrane filtering and EffectorP v3.0, the researchers identified an average of 336 candidate effectors per strain, the majority apoplastic. Orthology analysis condensed 6,330 effector proteins into 455 orthogroups, with 130 core effector families shared across the genus and only 17 strictly conserved in every strain, most of them of unknown function. The species-specific effector sets were enriched in adhesion, immunity and cuticle-interaction domains, and many B. brongniartii effectors matched experimentally validated virulence proteins from plant pathogens such as Magnaporthe oryzae, Colletotrichum gloeosporioides and Fusarium solani — evidence of convergent or repurposed virulence mechanisms spanning ecological boundaries.

Taken together, the study paints a picture in which host-range divergence in Beauveria is not achieved by discarding the core infection machinery — adhesion, germination, penetration, hemocoel proliferation — which remains largely intact and conserved. Instead, the specialist and the generalist differ in a compartmentalized set of genomic compartments: the secondary metabolite clusters that shape the chemical weapons deployed during infection, and a limited subset of lineage-restricted virulence factors governing surface interaction and immune evasion. The improved BIPESCO2 reference genome now gives researchers working on cockchafer biocontrol a solid genomic scaffold, while the identification of species-specific polyketide pathways and remodeled cyclodepsipeptide clusters offers a rich vein of unexplored chemistry — compounds whose biological roles, from insecticidal synergy to antimicrobial defense, now await experimental confirmation. For a genus upon which agriculture increasingly relies as synthetic pesticides face mounting restrictions, knowing exactly where the genetic levers of host specificity reside is a practical step toward designing more targeted, more predictable biological control agents.

The urgency behind the work is hard to overstate. Mosquito-borne pathogens impose a global burden measured in hundreds of millions of infections every year, and Aedes aegypti has expanded its footprint dramatically over recent decades, carried along by urbanization, international trade and a warming climate. The conventional response—synthetic chemical insecticides—is showing its age. Resistance to the organophosphate larvicide temephos has been documented across Southeast Asia and beyond, with resistant larvae overproducing detoxification enzymes such as cytochrome P450 monooxygenases and esterases. Residual insecticides can persist in soils and sediments, poison non-target aquatic organisms and accumulate along food chains, prompting health agencies to call for larvicides that are biodegradable, targeted and affordable. Researchers have responded by mining the living world for alternatives: plant extracts, bacterial metabolites, actinobacterial filtrates and, increasingly, the secretions of fungi that spend their lives attacking insects. The new study argues that these entomopathogenic fungi, long valued as living biocontrol agents, are also superb chemical factories for green nanotechnology.

Silver’s antimicrobial pedigree reaches back to antiquity, but its nanoscale incarnation behaves very differently from the metal in jewelry and tableware. Shrink silver to a few dozen nanometers and the proportion of atoms sitting on the particle surface skyrockets; those surface atoms interact directly with biological membranes and steadily release silver ions, the species responsible for much of the toxicity. Chemists can force this transformation with reagents such as sodium borohydride or citrate, but those routes typically demand hazardous chemicals, elevated temperatures and organic solvents. Biosynthesis sidesteps the problem. Filamentous fungi secrete a rich cocktail of extracellular enzymes, proteins and polysaccharides; when their cell-free culture filtrate meets an aqueous silver nitrate solution, those biomolecules reduce silver ions (Ag+) to neutral metallic atoms (Ag0), which nucleate into nanoparticles. Other proteins then adsorb onto the nascent particle surfaces and cap them, arresting further growth and stabilizing the colloid against aggregation. The fungus, in effect, performs the reduction, the shaping and the stabilization in a single, room-temperature step, using nothing more exotic than its own metabolism.

The two species were not chosen at random. Trichoderma asperellum is a soil-dwelling workhorse of agricultural biocontrol, famed for parasitizing plant pathogens and secreting an arsenal of secondary metabolites. Metarhizium anisopliae, the agent of the so-called green muscardine disease in beetles, actively infects insects and has served for more than a century as a mycoinsecticide. Where most previous mycosynthesis studies tested a single organism, the team also combined the two cultures, harvesting a mixed filtrate containing the proteins and metabolites of both before the reduction step. This combined system, designated Ta Ma AgNPs, yielded particles with properties distinct from either single-species batch—and, as the bioassays later confirmed, distinct biological behavior. The rationale, the authors suggest, is that pooling two different fungal secretomes can produce a more diverse biomolecular coating on the nanoparticle surfaces, potentially enhancing colloidal stability and biological activity in ways that neither organism achieves alone.

Characterization followed a demanding, multi-instrument protocol. Ultraviolet–visible spectroscopy detected the characteristic surface plasmon resonance of silver nanoparticles—the collective oscillation of conduction-band electrons that absorbs light in the visible spectrum—confirming that reduction had succeeded in all three systems. Attenuated total reflectance Fourier-transform infrared spectroscopy, or ATR-FTIR, mapped the functional groups of the proteins, carbohydrates and other biomolecules adsorbed onto the particle surfaces, direct evidence that fungal metabolites were acting as capping agents. Cryogenic field-emission scanning electron microscopy and cryogenic transmission electron microscopy—techniques that image flash-frozen specimens close to their native, hydrated state—revealed uniformly spherical particles in every preparation. The mean diameters measured by TEM were 9.17 nanometers for the Trichoderma-derived particles (Ta AgNPs), 11.25 nanometers for the Metarhizium-derived particles (Ma AgNPs) and 12.54 nanometers for the combined-fungal particles (Ta Ma AgNPs), all squarely within the size range associated with potent biological activity. Dynamic light scattering characterized the hydrodynamic dimensions of the particles in suspension, while zeta potential measurements, which quantify the effective surface charge of a colloid, ranged from −23 to −26.9 millivolts. Values of that magnitude imply strong electrostatic repulsion between particles, keeping them dispersed in water rather than clumping and settling—an indispensable property for any nanoparticle intended to be applied to mosquito breeding habitats.

With the materials verified, the team turned to the mosquito. Following World Health Organization guidelines for laboratory larvicidal testing, they exposed Aedes aegypti larvae to each formulation at four concentrations—25, 50, 100 and 150 micrograms per milliliter—and scored mortality at 24 and 48 hours, correcting for control mortality with Abbott’s formula and computing lethal concentrations by probit analysis. All three preparations proved potently larvicidal, but the combined-fungal particles led at every time point. Their 24-hour median lethal concentration (LC50) was 52.32 micrograms per milliliter, against 58.61 for Ta AgNPs and 63.39 for Ma AgNPs; by 48 hours the values had fallen to 39.50, 43.60 and 51.46 micrograms per milliliter, respectively. Equally telling, the nanoparticles outperformed the raw fungal filtrates from which they were made: mortality reached 82.50 percent for Ta AgNPs, 80.44 percent for Ma AgNPs and 87.69 percent for Ta Ma AgNPs, all higher than the killing achieved by unmodified fungal extracts. The silver was no passive carrier of fungal toxins; the particles themselves were the weapons.

How exactly do these particles dispatch a larva? The leading mechanisms assemble into a coherent picture. At nine to thirteen nanometers, the spheres can adhere to and penetrate the larval cuticle, the chitinous armor through which the insect breathes and senses its world. Once inside, silver nanoparticles and the ions they liberate attack a battery of cellular targets simultaneously: they bind sulfur- and phosphorus-rich biomolecules such as proteins and DNA, inhibit respiratory and antioxidant enzymes, and catalyze the generation of reactive oxygen species that oxidize membrane lipids and structural proteins. Studies of biosynthesized silver particles in mosquito larvae have documented disruption of the midgut epithelium, deranged ion regulation and characteristic aberrant swimming before death, typically within hours to days of exposure. The negative zeta potentials measured here suggest each particle carries a corona of anionic fungal proteins, which may promote adhesion to positively charged membrane surfaces—and may help explain why the dual-species corona of the combined batch proved most lethal of all. Mortality climbed steadily with both dose and exposure time, a pattern consistent with progressive, cumulative toxicity rather than any single-point kill mechanism.

The same particles were then pitted against four bacterial pathogens representing both major cell-envelope architectures: the Gram-negatives Escherichia coli and Pseudomonas aeruginosa and the Gram-positives Bacillus megaterium and Staphylococcus aureus. Using the zone-of-inhibition well diffusion method and benchmarking against the antibiotic chloramphenicol, the researchers found that all three formulations inhibited P. aeruginosa and B. megaterium, with the clearest effect at the highest dose of 150 micrograms per milliliter. Activity against Pseudomonas is particularly noteworthy. P. aeruginosa is an opportunistic pathogen shielded by a restrictive outer membrane and a formidable talent for biofilm formation, and it ranks among the multidrug-resistant bacteria for which new agents are most urgently sought. Silver nanoparticles are believed to act through multiple, simultaneous mechanisms—membrane disruption, ion release, protein denaturation, oxidative stress and interference with DNA replication—which together make comprehensive bacterial resistance far harder to evolve than it is against single-target antibiotics. The differences observed among the four species likely reflect their contrasting cell-wall structures and the distinct biomolecular coatings of each nanoparticle batch, and the authors suggest that this dual larvicidal and antibacterial profile positions the formulations as a two-in-one tool for mosquito-borne disease control and antimicrobial applications alike.

None of this means silver-spiked water will be sprayed across tropical neighborhoods tomorrow. The work remains laboratory-scale, and the road from beaker to breeding ground is long. Silver nanoparticles can themselves harm non-target aquatic organisms, and questions of environmental persistence, accumulation and dose escalation in real water bodies must be resolved before any field deployment; the formulations would also need to survive sunlight, dilution and microbial degradation in open habitats, and to be manufactured at scale at tolerable cost. The authors do not claim otherwise. What the study does establish is that fungal biosynthesis can reliably deliver nanoparticles of tightly controlled size, negative surface charge and robust colloidal stability—and that combining two entomopathogenic species produces a particle that outperforms those made by either fungus alone, both as a larvicide and as an antibacterial. As dengue incidence climbs across Asia, Africa and Latin America and insecticide resistance erodes the frontline tools of vector control, the image of two humble molds, grown side by side in a culture flask, quietly manufacturing a dual-purpose weapon against mosquitoes and bacteria alike is precisely the kind of biological ingenuity the field has been hunting for. Corresponding author Titik Kartika and colleagues conclude that the combined Ta Ma nanoparticles, above all, stand out as a candidate alternative strategy for mosquito-borne disease control—and, from the same flask, a possible ally in the broader fight against antimicrobial resistance.